Generally, useful products such as amino acids can be produced by a fermentation method using microorganism strains developed via artificial mutation or genetic recombination. In particular, in developing microorganism strains for large-scale production of amino acids, it will be beneficial to discover genetic factors, which are directly/indirectly involved in a higher cascade step of the production, and appropriately utilize them to develop microorganism strains capable of producing higher yields. A representative technology in this regard may be global transcription machinery engineering (gTME), which can regulate the expression of all intracellular genes by causing random mutations on recruiting protein of RNA polymerase.
RNA polymerase is a macromolecule comprised of five subunits of 2α, β, β′, and ω, and its holoenzymes are expressed as α2ββ′ω. Along with these holoenzymes, sigma (σ) factors, which are transcription initiation factors present in prokaryotes, can allow specific binding of RNA polymerase to promoters, and can be distinguished by their molecular weight. For example, σ70 stands for a sigma factor having a molecular weight of 70 kDa (Gruber™, Gross C A, Annu Rev Microbiol. 57: 441-66, 2003).
Escherichia coli is known to possess a housekeeping sigma factor σ70 (RpoD), a nitrogen-limitation sigma factor σ54 (RpoN), a starvation/stationary phase sigma factor σ38 (RpoS), a heat shock sigma factor σ32 (RpoH), a flagellar sigma factor σ28 (RpoF), an extracytoplasmic/extreme heat stress sigma factor σ24 (RpoE), a ferric citrate sigma factor σ19 (FecI), etc. These various sigma factors are known to be activated under different environmental conditions, and these characterized sigma factors can bind to the promoters of genes transcribed under specific environmental conditions, and thereby regulate the transcription of the genes. Studies on the increase of productivity of target materials by allowing random mutations on sigma factor 70 have been reported (Metabolic Engineering 9. 2007. 258-267), and there is also a study report on the enhanced tyrosine production using gTME technology in E. coli (U.S. Pat. No. 8,735,132).